1. Subject of the Invention
The invention refers to a video monitor for autostereoscopic imaging of three dimensional images or scenes in which the stereoscopic views are adaptively controlled according to the position of an observer in front of the monitor. The most important application of this 3D monitor is foreseen to be microsurgery and computer tomography in which the viewing of the third depth dimension to the observer will be a big advantage to the user who does not want to carry disturbing additional eye-glasses. Objects to be analyzed or micro-mechanically manipulated then appear before or behind the screen in the correct 3D position. The 3D presentation is based on two channel signal processing giving the different views of objects for the left and right eye corresponding to the observer position. The whole system for a person-adaptive monitor consists of the monitor itself, of a head-tracking device and a (real-time) graphic computer. The full stereoscopic adaptation is carried out electronically for one person by real time head-tracking processing without physical movements of devices. Further application could be 3D TV when a two channel transmission will be installed. For compatibility reasons switching on and off of 3D effects should be possible.
2. State of the Art
Stereoscopic methods of filming and projecting have been in use for years. Most methods use polarizing light (horizontally, vertically and circularly) in order to separate the right from the left picture. Verhulst, A. G.: Display and pick-up device for stereoscopic picture display: European Patent 0 332 268 (1988). The development of LCD-technologie has made feasible electronic control of the light-transmission of crystals. This has made possible the shutter-technique, which alternatingly makes the left and right glass of shutter-glasses non-light transmissive and synchronously displays the right and left picture sequentially on the monitor S. Hentschke, A. Herrfeld, C. Junge, R. Kothe: Stereoskope Echtzeitbildverarbeitung. CeBIT Exponat und Broschure (1994).
Autostereoscopic projections are realized by means of projection panels with stripe lens grids from different projection directions. Each perspective picture is then fitted to the correct projection direction, R. Bomer. Autostereoscopic 3-D Imaging by Front and Rear Projection and on Flat Panel Displays. Displays, Vol. 14, No. 1 (1993), pp. 39-46. However, it is almost impossible to achieve a continuous transition from one view to the next, for the number of projection directions cannot be enlarged arbitrarily. With an autostereoscopic display aimed at one single user, only two perspectives are used, that require a certain direction of viewing, Sheat D E, Chamberlin G R, Gentry P, Leggat J S, McCartney D J: 3-D Imaging Systems for Telecommunications Applications. Proc. SPIE, Vol.1669, p.186. Electronic Imaging Systems and Applications Meeting, San Jose (1992)--and "[7]" with--R. Borner: Autostereoskope Ruckprojektions--und Flachbildschirme. Fernseh--und Kinotechnik Bd. 48, Nr. 11 (1994). S. 594-600, [7]. A fully stereoscopic picture like in a hologram is achieved by use of "head tracking sensors" that control the high-capacity real-time computer for calculation of the fitting stereoscopic perspective on the one hand, and on the other hand control the autostereoscopic display for mechanical adjustment of the lens grid shield. It detects the exact position and movement of the observer's head and simultaneously generates the fitting pictures. Furthermore, expensive VR-Systems (Virtual Reality) utilizing "Head Mounted Displays" are in use.
Nuclear Magnetic Resonance and Computed Tomography are the most important fields of application of stereoscopic 3D-imaging in medical engineering. In order to calculate certain perspectives needed, high-performance computers are being developed for "Volume Tracking Algorithms" H. P. Mainzer, Meetz, D. Scheppelmann, U. Engelmann, H. J. Bauer: The Heidelberg Ray Tracing Model. IEEE Computer Graphics and Appl. November 1991 pp. 34ff. The combined computed visualization and real-time transmission of endoscopes are becoming a very important neuro-surgical tool. Stereoscopic endoscopes are currently in use already. It will be easy to combine an infrared based "head tracking sensor" with an observer-adaptive autostereoscopic monitor system for electronic control of movement.
A Person-Adaptive Autostereoscopic Shutter Screen (PAAS) is known from S. Hentschke, Personenadaptiver autostereoskoper Shutter Bildschim (PAAS). Patentschrift DE 19500315 C, (1995). But it needs a fast double display technology which is not yet available today. Another autostereoscopic display has been shown in Alio, Pierre: Dispositif et systeme video autostereoscopique. Demande de Brevet d'invention, Numero de publication: 2 705 008. But this one is not adaptive with respect to the observer position; it is based on fixed viewing directions (preferably 4). Hence a correct autostereoscopic view is only possible from some fixed positions.
3. Problem To Be Solved
To get a comfortable presentation of 3D images an autostereoscopic method is necessary. The position of the user must not be restricted to one point in front of the monitor but the movement of the observer's head should be used to be able to observe a 3D object from different points of view. This makes necessary to apply an adaptive system which, of course, must be oriented to only one person. The further problem to be solved is to find a pure electronical adaptive control of the observer's position and autostereoscopic view to avoid maintenance problems and micro-mechanical movements of lenticular lens screens in known systems S. Hentschke: Personenbezogener autostereoskoper Bildschirm. Patentanmeldung P 44 33 058.8 (1994). A wide application field is of importance to achieve high volumes and low prices of such an adaptive autostereoscopic system. In addition a double-display solution should be avoided which is used for example in an autostereoscopic Shutter method cf. S. Hentschke, Personenadaptiver autostereoskoper Shutter Bildschim (PAAS). Patentschrift DE 19500315 C, (1995).
Up to now, there are known no adaptive autostereoscopic monitors that can be built an the basis of conventional monitors to which can be added different supplementary electronical and physical components to get easily an autostereoscopic system. This problem is to be solved by this invention.